DE 699 23 847 T2 discloses a process for manufacturing an optical mold body from thermoplastic resin by injection pressure molding, wherein the volume of a mold cavity expands more strongly than the volume of the optical mold body in question, and wherein molten thermoplastic resin is injected into the mold cavity through an injection molding passage. In the expanded mold cavity, the material is subsequently pressed to a predetermined thickness of the medial area of the mold body or to a thickness which is by up to 200 μm smaller than the predetermined thickness. After pressing of the material in the expanded cavity, the pressure of the resin in the injection molding passage and the molding pressure in the mold cavity are changed within such boundaries that the width of change does not exceed ±100 μm of the predetermined thickness of a medial area of the mold body in order to be able to obtain the predetermined thickness of the finished mold body. Subsequently, the molten thermoplastic resin is retained within the mold cavity for sufficient time until the mold body in question has been formed. Thereafter, the thus obtained mold body is removed from the mold cavity.
According to DE 699 23 847 T2, a method for manufacturing an optical mold body from thermoplastic resin by injection pressure molding as described in U.S. Pat. No. 4,540,534, EP 0 640 460 and JP 9-057794 has to be distinguished there from, which method comprises                expanding the volume of a mold cavity beyond the volume of the optical mold body in question,        injection molding of molten thermoplastic resin in(to) the mold cavity through an injection molding cylinder,        pressing the expanded cavity to a predetermined thickness of the mold body,        returning a surplus of the thermoplastic resin which has occurred by the molding step, into the injection molding cylinder,        leaving the molten thermoplastic resin in the mold cavity until the mold body in question has been shaped, and        removing the obtained mold body from the mold cavity.        
DE 102 20 671 A1 discloses a plastic lens consisting of a collective lens of plastic material having a high Abbé number, and a dispersion lens connected therewith integrally and in positive fit of plastic material having a comparably low Abbé number regarding the plastic material of the collective lens, wherein the thermal expansion coefficients of the plastic materials are essentially the same.
Headlight lenses are known e.g. from WO 02/31543 A1, U.S. Pat. No. 6,992,804 B2, WO 03/074251 A1 and DE 100 52 653 A1. Further vehicle headlights are known e.g. from DE 100 33 766 A1, EP 0 272 646 A1, DE 101 18 687 A1 and DE 198 29 586 A1.
It is an object of the invention to reduce the costs for manufacturing lens elements, in particular elements for illumination purposes, particularly for the manufacturing of headlight lenses for vehicle headlights. In this context it is particularly desirable to manufacture especially high-value lens elements, in particular headlight lenses. It is a further object of the invention to improve the process disclosed in DE 10 2007 037 204 A1. In this context, it is particularly aimed at achieving a higher accuracy of contour.